The goal of this project is to define immune mechanisms and viral characteristics important in the pathogenesis of Aleutian disease (AD). Monoclonal antibodies were used to study antigenic differences among ADV isolates. Antibodies with three predominant patterns of reactivity have been identified: 1) those that react with viral antigens extracted from tissues of infected mink, 2) those that react with viral antigens purified from ADV infected cell cultures, and 3) those that react with virus from either source. Antibodies recognizing viral antigens purified from ADV infected cell cultures recognize the major viral structural proteins of ADV while the viral associated antigen recognized by monoclonal antibodies reacting with tissue extract has not been determined. These reagents allow more precise characterization of ADV isolated than has been possible previously. We are also using them as probes to localize viral antigen in tissues of infected mink. Spleen, liver, lymph node and kidney from infected mink have been examined so far but as yet no viral antigen has been demonstrated. Techniques will be modified and further attempts made in this regard. Additional monoclonal antibodies will also be used and new ones developed.